Materials which are used in bioactive contexts often contain phases of differing character. Specifically, any of the included phases may have a large tendency for decomposition at the production, which for metals and especially ceramics take place at an elevated temperature. This commencing thermally activated decomposition may have a directly negative effect on the end product, for example by formation of gaseous compounds which form pores that acts as defects, especially from a strength point of view, or by contributing to the formation of new unwanted phases. A related effect is that decomposition of the phase with a tendency for decomposition is catalysed by the presence of another phase, for example an oxide, which leads to decomposition at temperatures which considerably decrease those for the corresponding pure material with a tendency for decomposition. The presence of an oxide or metal in the bioactive composite material is necessary in order to improve the mechanical properties in relation to pure apatite.
Other related aspects, which however do not concern the basic area of the present application, are e.g. treated, besides in the literature, in the following patents/patent applications: U.S. Pat. No. 3 789 900, DE 330122, U.S. Pat. No. 4 149 893, U.S. Pat. No. 4 957 674, U.S. Pat. No. 4 599 085, DE 29 28 007 Al and JP 62-142 565.